This invention relates to improvements in a dual inline package switch assembly (hereinafter referred to as a DIP switch) for use in encoders, decoders, and other electronic computer components.
FIG. 1 is a sectional view showing a conventional DIP switch which comprises a housing including a switch case 1 and a base plate 2 enclosing the open bottom of the switch case 1. A fixed contact 3 is fixed on the base plate 2 and has its leg extending outwardly through the base plate 2. A movable contact 4 formed of a resilient metal plate has its leg extending outwardly through the base plate 2. A slider 5 is provided for sliding movement within the housing to bring the movable contact 4 into and out of contact with the fixed contact 3. The slider 5 has an operating knob 5a extending outwardly from its upper surface through an elongated slit 1a formed in the upper surface of the top wall of the switch case 1. The slider 5 has on its upper surface projections 5b which are selectively engaged in respective recesses 1b formed in the inner surface of the top wall of the switch case 1 when the switch is in open or closed state. Since the slider 5 is restrained from movement, due to engagement of one of the projections 5b in one of the recesses, the projection must be disengaged from the recess 1b with a relatively large force before the slider 5 is moved to cause the switch to be changed from the state to the other state.
With such a detent mechanism, vibrations occurring in the direction normal to the direction of movement of the slider 5, cause variations in the contact pressure between the fixed and movable contacts 3 and 4, which results in unstable switching operations.
FIG. 2 is a sectional view showing another conventional DIP switch which comprises a housing including a switch case 1 and a base plate 2 enclosing the open bottom of the switch case 1. A pair of fixed contacts 3 are fixed on the base plate 2 and have their legs extending through the base plate 2. Each of the fixed contacts 3 has a protruded end portion 3a which faces the protruded end portion of the other fixed contact in spaced relation. A slider 5 is provided for sliding movement within the housing and formed in its lower surface with a recess 5d containing therein a resilient short strip 4 having a protruded portion 4a which is engaged between the protruded end portions 3a of the fixed contacts 3 when the switch is in its closed state. Since the slider 5 is restrained from movement due to engagement of the protruded portion 4a of the short strip 4 between the protruded end portions 3a of the fixed contacts 3, the protruded portion 4a must be disengaged from the gap between the protruded portions 3 a with a relatively large force when the switch is required to open.
The shortcoming, as described in connection with FIG. 1, is encountered with such a detent mechanism of FIG. 2.
FIG. 3 is a schematic view showing still another conventional DIP switch which comprises a base plate 2 formed of plastic or any other suitable resin, a pair of resilient contacts 3 and 4 having their legs 3a and 4a extending through the base plate 2 and supported to have their contact portions 3b and 4b held in pressure contact with each other, and a slider 5 having on its one side surface a projection 5c extending in the direction of movement of the slider 5 for insertion between the contact portions 3b and 4b to disconnect them.
One of the difficulties with such a conventional DIP switch is that the base plate 2 is subject to thermal deformation to change the relative position of the contacts when the contact legs 3a and 4a are soldered to electrical circuit openings. This causes reduction in contact pressure, which results in unstable switching operations.
FIG. 4A is a top plan view showing still another conventional DIP switch and FIG. 4B is a view partly in elevation and partly in section of the DIP switch of FIG. 4A. The DIP switch comprises a plurality of sliders 5 contained within a housing 1. Each of the sliders 5 has on its upper surface an operating knob 5a extending upwardly through a slot 1a formed on the upper wall of the housing 1. Since gaps G exist between the housing 1 and the sliders 5, detergent will enter into the switch housing 1 to cause troubles in switching operation when the switch is washed with a detergent after it is attached on a printed circuit board.